1. Field of the Invention
The present invention relates to an ink composition for ink jet recording and an ink jet recording method wherein ink droplets are ejected from a recording head to yield an ink image on a recording medium.
2. Background Art
Ink jet recording is a printing method wherein droplets of an ink composition are ejected and deposited onto a recording medium, such as paper, to conduct printing. This method has a feature that an image having high resolution and high quality can be printed at a high speed by means of relatively inexpensive apparatuses. In general, the ink composition used in the ink jet recording comprises water as a main component and, added thereto, a colorant and a wetting agent, such as glycerin, for preventing clogging and other purposes.
One of the problems to be solved in the ink jet recording method is feathering. Further, for example, good rapidity in drying of prints, good printing on various recording media, and, in the case of multi-color printing, freedom from bleeding of the ink from color to adjacent colors are required of inks for ink jet recording.
Various methods have been proposed in order to realize good images free from feathering or bleeding. For example, Japanese Patent Laid-Open Nos. 288042/1987, 330032/1993, and 126952/1994 disclose ink jet recording methods wherein a recording medium is heated during or immediately before printing.
In these methods, the recording medium is heated to evaporate the solvent component in dots on the recording medium by heat energy to reduce feathering of the ink and, at the same time, to improve the fixation of printed images.
The heating of the recording medium, however, has a fear of causing a failure of the ink jet head close to the recording medium to eject the ink, heat distortion of the recording medium and the like. Therefore, measures should be taken to avoid these unfavorable phenomena. Further, there is an ever-increasing demand for an increase in printing speed and an increase in quality. In addition, an ink jet recording method, with higher efficiency, involving heating of the recording medium has been still desired in the art from the viewpoint of energy saving.
The present inventors have now found that a combination of an ink composition containing a certain compound with an ink jet recording method, wherein a recording medium is heated at a temperature of or above the cloud point of the compound, can realize very good images with high efficiency. The present invention has been made based on such finding.
Accordingly, it is an object of the present invention to provide an ink jet recording method which can efficiently realize good images, particularly an ink jet recording method which can realize, on plain papers, high-quality prints free from feathering or bleeding at a relatively low heating temperature, and an ink composition for use in this method.
According to one aspect of the present invention, there is provided an ink composition for an ink jet recording method comprising the step of ejecting droplets of an ink composition and depositing the droplets onto a heated recording medium,
the ink composition comprising at least a colorant, a water-soluble organic solvent, water, and at least one compound represented by formula (I),
the colorant being present in the state of dispersion in the ink composition,
the surface of the heated recording medium having a temperature of or above the cloud point of the compound represented by formula (I):
Rxe2x80x94[0xe2x80x94(EO)mxe2x80x94(PO)n]xe2x80x94H
xe2x80x83wherein
EO represents an ethyleneoxy group;
PO represents a propyleneoxy group;
m and n are each an integer; and
R represents CKH2k+1 wherein k is a natural number of 4 to 18,
EO and PO being arranged, regardless of order in the parentheses, randomly or as blocks joined together.